Answer:
x = 15
Step-by-step explanation:
the opposite angle of a cyclic quadrilateral sum to 180° , then
6x + 20 + 3x + 25 = 180
9x + 45 = 180 ( subtract 45 from both sides )
9x = 135 ( divide both sides by 9 )
x=15º
Sum of quadrilateral interior angles;
(4x + 25) + (3x + 25) + (6x + 20) + 180-(4x + 25)=360
3x + 25 + 6x + 20 + 180 =360
9x = 360 - 225
9x = 135
x = 15º
